Voluminous fiber laminates and their production

ABSTRACT

A voluminous fiber laminate is described, which contains one or more layers of an absorbent fibrous material, which is compacted through water needling, between at least two carrier nonwoven materials, it having areas having higher needling density and areas having lower needling density over the entire area of the fiber laminate to form a quilted structure. A device cited for this purpose is distinguished in that the water needling unit also has, in addition to nozzle strips having a large number of nozzles per unit area, nozzle strips having a lower number of nozzles, or one or more nozzle strips are dispensed with completely.

The object of the present invention is voluminous fiber laminates, which contain one or more layers of an absorbent fibrous material which is compacted through water needling, as well as a method and a device for their production.

A method for producing a composite nonwoven material from at least one carrier nonwoven material, e.g., a spunbond nonwoven material, and a wood pulp layer laid on this carrier nonwoven material to produce a high gene product, is known from EP 1 250 482 B1, the spunbond nonwoven material being compressed dry, before the coating with the super absorbent material, for precompaction, the woodpulp layer then being applied and both being compacted together using hydrodynamic water needling and then dried.

Furthermore, a method for producing a fiber laminate, in particular an absorbent wiping cloth, is known from EP 1 445 366 A2, at least one spunbonded fabric being precompacted and at least one fibrous layer made of hydrophilic fibers being applied to the precompacted spunbonded fabric. The laminate made of spunbonded fabric and fibrous layer is then hydrodynamically compacted.

Finally, a fiber laminate, in particular an absorbent cleaning cloth made of at least one precompacted spunbonded fabric made of elements and made of at least one fibrous layer made of hydrophilic fibers, which is hydrodynamically compacted, is known from EP 1 524 350 A1, embossed deformations being introduced into the surface of the hydrodynamically compacted fiber laminate. During the production of this type of absorbent wiping and cleaning cloths, the two outer layers made of precompacted spunbonded fabrics and the inner layer made of air laid pulp are bonded to one another by waterjet compaction.

Products of this type are superior in regard to cost and strength to the wiping and cleaning cloths produced from carded fiber nonwoven materials, but in practice their thickness, which is too low, and thus their absorption capability are faulted. Until now, the delamination resistance of the individual layers was also insufficient due to too little waterjet compaction at acceptable power consumption, so that above all in the moistened state, the layers could be easily separated from one another. This disadvantage-was improved by the pre-embossing of the nonwoven layers used or through later embossing of the final product compacted by waterjet in the above-mentioned EP 1 445 366 A2 and EP 1 524 350 A1. Therefore, the object presents itself of searching for alternative methods for producing voluminous and absorbent fiber laminates which provide a thicker and less sensitive product, in particular a wiping and/or cleaning cloth, or are also suitable for other applications having high absorption requirements.

The object of the present invention is therefore a voluminous fiber laminate containing one or more layers of an absorbent fiber material between at least two carrier nonwoven materials, which is compacted through water needling, in which areas having higher needling density and areas having lower needling density are provided over the entire area of the fiber laminate to form a quilted structure. During its production, a production increase is achieved in comparison to the previously known methods with the same energy use through elevated production speed or a lower energy use is achieved-at the same production quantity.

Greatly varying carrier nonwoven materials may be used for this product. Nonwoven materials compacted through thermal calendering, through hot air compaction, and through mechanical needling or chemical treatment are suitable. Nonwoven materials obtained from a spinning, air/wet laid, or carding process are also suitable. Nonwoven materials made of homofibers, bicomponent, multicomponent, or mixed fibers may also be used. Carrier nonwoven materials made of polyolefins such as polypropylene, polyethylene, or polyamide or polyester, but also made of natural or converted natural materials such as cellulose, wool, cotton, or lyocell and viscose, have also proven themselves.

The absorbent fibrous material used in the voluminous fiber laminate according to the present invention may comprise all hydrophilic fibrous materials, all products known as super absorbers being outstandingly suitable.

For the production of the carrier nonwoven materials, according to the present invention, preferably filaments having a fineness and/or a diameter of 0.3 to 3 denier, preferably 0.5 to 2.5 denier, and very preferably 0.8 to 1.5 denier are used. The fineness and/or the diameter of the filaments of the carrier nonwoven materials is more expediently below 1.5 denier. Voluminous fiber laminates which comprise multiple nonwoven layers and/or filament layers are-also an object of the present invention. The filaments of the individual layers may also have different properties in this case.

A special device has been developed to produce the voluminous fiber laminate according to the present invention. It comprises a spin bonding or carding unit, an air compaction or calender unit, a possibly directly adjoining unit for applying the absorbent fibrous material to the precompacted nonwoven material, and a water needling unit. According to the present invention, this water needling unit has nozzle strips having a large number of nozzles per unit area, followed by nozzle strips having a lower number of nozzles. According to the present invention, in comparison to the related art up to this point, a water beam may also be dispensed with completely, through which investment costs may be saved. The production of the fiber laminate may also occur on off-line facilities according to the present invention, i.e., previously produced coiled cover nonwoven materials are supplied to the application of the absorbent fibrous material and the waterjet compaction through unrolling.

A large number of nozzles per nozzle strip is to be understood as approximately 40 nozzles which are situated next to one another per inch width of the nozzle strip. These nozzles typically have a diameter around 0.12 mm. In contrast, nozzle strips having a lower number of nozzles are to be understood as those which have only approximately 20 or fewer nozzles per inch width of the nozzle strip. The spacing of the nozzle strip is to be tailored, at 5 to 20 holes per inch, to the spacing of the calender points when using a thermally compacted (calendered) (spunbonded) nonwoven material, at 1.5 to 3 times, preferably 2 to 2.5 times greater than this spacing scale. The diameter of these nozzles is expediently at least 0.14 mm, preferably 0.18 mm. Through the larger diameter, the quantity of water per nozzle is increased, with the effect of more intensive bonding of the layers to one another. This results in the effect that the stop lines, which generate a quilted structure, are formed, which are sufficient to prevent delamination of the composite.

This one nozzle strip operates from one side and thus generates an asymmetrical product. If this asymmetry is to be prevented, the possibility of using two nozzle strips exists. These operate in opposite directions, i.e., on the top or bottom of the product in each case and are each equipped with approximately half of the number of nozzles per inch width of the one nozzle strip. In this case, a transverse movement of these two nozzle strips toward one another is recommended in order to avoid continuous spacing errors of the two nozzle systems to one another. The power consumption in the production changes only insignificantly in this case.

In comparison to the normally used number of 40 nozzles per inch width of the nozzle strip, the number of nozzles on the nozzle strips used according to the present invention having a lower number of nozzles is at most only half as large in relation thereto. However, it is also possible to dispense with one or more nozzle strips completely and thus concentrate the needling on very specific areas of the laminate. A laminate having a quilted structure arises in this way.

A device according to the present invention for producing the voluminous fiber laminate according to the present invention is shown in the attached drawing.

The endless fibers 2 continually exiting from the device 1 are incident on the endless band 3 running on the bottom, which runs in the direction of the arrow. A calender mill 5 is assigned to this endless band 3, which—if desired—may also provide a finely embossed compacted nonwoven material by applying power and heat. The calender unit may also be replaced by an air compaction unit (not shown here). After this method step, the absorbent fibrous material is applied using a device 6. A second carrier nonwoven material, which is formed in the device 10 and the calenders 11, is then laid as the upper cover nonwoven material on the absorbent fibrous material and the layered material thus resulting is applied to the water needling.

Multiple needling drums 13, 14 situated one after another, which the material travels around in a meandering way and each of which has the nozzle bars, indicated with arrows, assigned to it from above, are used for this purpose. The subsequent drying may be performed using ventilation dryers 9, whose screen drums 9′ have the ventilator externally assigned to them. Subsequently, there may also be a pass through the calenders 15, 16 here, in which both rolls 15 and 16 are then to be heated.

The production method for the voluminous fibrous nonwoven already illustrated by the description of the device is thus distinguished in that one or more layers of an absorbent fibrous material are compacted between the carrier nonwoven materials through waterjet needling and areas having a higher needling density and areas having lower needling density are generated over the entire area of the composite nonwoven material while forming quilted structures. Multiple nonwoven material layers may also be laid one on top of another on the laminate in this case. In any case, the multilayer laminate is bonded through waterjet needling and subsequently dried.

It is decisive for the method according to the present invention that in contrast to the related art, the entire area of the fiber laminate is not needled uniformly, but rather specific regions are strongly needled and other areas are compacted less or not at all. These areas which are not needled may then assume a very voluminous form. The resulting product is thus distinguished by the following advantageous features:

1. it displays a greater thickness and absorption capability than a completely needled fiber laminate;

2. it displays better delamination resistance than the wiping and cleaning cloths previously produced through needling, since the areas having increased needling, stop the delamination due to their strong compaction;

3. a stretching reserve results in the transverse direction due to the curved cover layers, through which the voluminous fiber laminate becomes more elastic and softer. 

1. A voluminous fiber laminate containing one or more layers of an absorbent fibrous material, which is compacted through water needling, between at least two carrier nonwoven materials, characterized in that it has areas having higher needling density and areas having lower needling density over the entire area of the fiber laminate to form a quilted structure.
 2. A cleaning or wiping cloth comprising a voluminous fiber laminate according to claim
 1. 3. A device for producing a voluminous fiber laminate according to claim 1, comprising one or more spin bonding or carding unit(s), one or more air compaction or calender unit(s), a possibly directly adjoining unit for applying absorbent fibrous material to the precompacted fibrous nonwoven material and a water needling unit, characterized in that the water needling unit also has, in addition to nozzle strips having a large number of nozzles per unit area, nozzle strips having a lower number of nozzles, or a water beam is dispensed with completely.
 4. A method for producing a voluminous fiber laminate made of composite nonwoven materials, in which one more layers of an absorbent fibrous material are compacted through waterjet needling between the carrier nonwoven materials, characterized in that areas having higher needling density and areas having lower needling density are generated over the entire area of the composite nonwoven material to form quilted structures. 